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<body class="article toc2 toc-left">
<div id="header">
<h1>Quick Guide</h1>
<div class="details">
<span id="revnumber">version 3.9.6,</span>
<span id="revdate">2019-04-06</span>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Features</div>
<ul class="sectlevel1">
<li><a href="#_what_is_picocli">1. What is picocli</a></li>
<li><a href="#_how_to_use_it">2. How to Use it</a></li>
<li><a href="#_options_and_parameters">3. Options and Parameters</a></li>
<li><a href="#_strongly_typed_everything">4. Strongly Typed Everything</a></li>
<li><a href="#_required_arguments">5. Required Arguments</a></li>
<li><a href="#_multiple_values">6. Multiple Values</a></li>
<li><a href="#_help_options">7. Help Options</a></li>
<li><a href="#_version_help">8. Version Help</a></li>
<li><a href="#_usage_help">9. Usage Help</a></li>
<li><a href="#_ansi_colors_and_styles">10. ANSI Colors and Styles</a></li>
<li><a href="#_subcommands">11. Subcommands</a></li>
<li><a href="#_reuse">12. Reuse</a></li>
<li><a href="#_parsing">13. Parsing</a></li>
<li><a href="#_tracing">14. Tracing</a></li>
<li><a href="#_tab_autocomplete">15. TAB Autocomplete</a></li>
<li><a href="#_more">16. More</a></li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>This is the Quick Guide. For more detail, see the full user manual at <a href="http://picocli.info">http://picocli.info</a>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_what_is_picocli">1. What is picocli</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Picocli is a Java library and mini-framework for creating command line applications with almost no code.</p>
</div>
<div class="paragraph">
<p>Picocli supports a variety of command line syntax styles including POSIX, GNU, MS-DOS and more.
It generates highly customizable usage help messages with <a href="#_ansi_colors_and_styles">ANSI colors and styles</a>.
Picocli-based applications can have <a href="autocomplete.html">command line TAB completion</a> showing available options, option parameters and subcommands, for any level of nested subcommands.</p>
</div>
<div class="paragraph">
<div class="title">Example usage help message</div>
<p><span class="image"><img src="images/ExampleUsageANSI.png" alt="Screenshot of usage help with Ansi codes enabled"></span></p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_how_to_use_it">2. How to Use it</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Create a class and annotate its fields or methods with <code>@Option</code> or <code>@Parameters</code> to declare what options and positional parameters your application expects.
While parsing the command line, picocli will initialize these fields based on the command line arguments.
If your class implements <code>Runnable</code> or <code>Callable</code>, you can let picocli kick off your application after parsing is successfully completed.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
For applications that cannot use the annotations, there is also a <a href="picocli-3.0-programmatic-api.html">programmatic API</a> for defining what options and positional parameters to expect, and a programmatic API for handling parse results. The programmatic API is not covered in this Quick Guide.
</td>
</tr>
</table>
</div>
<div class="sect2">
<h3 id="_example">2.1. Example</h3>
<div class="paragraph">
<p>Here is a small example application that uses the <code>CommandLine.call</code> <a href="#_runnable_and_callable">convenience method</a>
to do parsing and error handling in one line of code. The <a href="#_mixin_standard_help_options">mixinStandardHelpOptions</a> attribute
adds usage help and version help options your application.</p>
</div>
<div id="CheckSum-application" class="listingblock">
<div class="title">Example <code>Callable</code> application</div>
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Prints the checksum (MD5 by default) of a file to STDOUT.</span><span class="delimiter">&quot;</span></span>,
         name = <span class="string"><span class="delimiter">&quot;</span><span class="content">checksum</span><span class="delimiter">&quot;</span></span>, mixinStandardHelpOptions = <span class="predefined-constant">true</span>, version = <span class="string"><span class="delimiter">&quot;</span><span class="content">checksum 3.0</span><span class="delimiter">&quot;</span></span>)
<span class="type">class</span> <span class="class">CheckSum</span> <span class="directive">implements</span> <span class="predefined-type">Callable</span>&lt;<span class="predefined-type">Void</span>&gt; {

    <span class="annotation">@Parameters</span>(index = <span class="string"><span class="delimiter">&quot;</span><span class="content">0</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">The file whose checksum to calculate.</span><span class="delimiter">&quot;</span></span>)
    <span class="directive">private</span> <span class="predefined-type">File</span> file;

    <span class="annotation">@Option</span>(names = {<span class="string"><span class="delimiter">&quot;</span><span class="content">-a</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--algorithm</span><span class="delimiter">&quot;</span></span>}, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">MD5, SHA-1, SHA-256, ...</span><span class="delimiter">&quot;</span></span>)
    <span class="directive">private</span> <span class="predefined-type">String</span> algorithm = <span class="string"><span class="delimiter">&quot;</span><span class="content">SHA-1</span><span class="delimiter">&quot;</span></span>;

    <span class="directive">public</span> <span class="directive">static</span> <span class="type">void</span> main(<span class="predefined-type">String</span><span class="type">[]</span> args) <span class="directive">throws</span> <span class="exception">Exception</span> {
        CommandLine.call(<span class="keyword">new</span> CheckSum(), args);
    }

    <span class="annotation">@Override</span>
    <span class="directive">public</span> <span class="predefined-type">Void</span> call() <span class="directive">throws</span> <span class="exception">Exception</span> {
        <span class="type">byte</span><span class="type">[]</span> fileContents = Files.readAllBytes(file.toPath());
        <span class="type">byte</span><span class="type">[]</span> digest = <span class="predefined-type">MessageDigest</span>.getInstance(algorithm).digest(fileContents);
        <span class="predefined-type">System</span>.out.println(javax.xml.bind.DatatypeConverter.printHexBinary(digest));
        <span class="keyword">return</span> <span class="predefined-constant">null</span>;
    }
}</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_options_and_parameters">3. Options and Parameters</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Command line arguments can be separated into <em>options</em>  and <em>positional parameters</em>.
Options have a name, positional parameters are usually the values that follow the options,
but they may be mixed.</p>
</div>
<div class="paragraph">
<p><span class="image"><img src="images/OptionsAndParameters2.png" alt="Example command with annotated @Option and @Parameters"></span></p>
</div>
<div class="paragraph">
<p>Picocli has separate annotations for options and positional parameters.</p>
</div>
<div class="sect2">
<h3 id="_options">3.1. Options</h3>
<div class="paragraph">
<p>An option must have one or more <code>names</code>.
Option names commonly start with <code>-</code> or <code>--</code>, but picocli lets you use any option name you want.</p>
</div>
<div class="paragraph">
<p>The below example shows options with one or more names, options that take an option parameter, and a <a href="#_help_options">help</a> option.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="type">class</span> <span class="class">Tar</span> {
    <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-c</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">create a new archive</span><span class="delimiter">&quot;</span></span>)
    <span class="type">boolean</span> create;

    <span class="annotation">@Option</span>(names = { <span class="string"><span class="delimiter">&quot;</span><span class="content">-f</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--file</span><span class="delimiter">&quot;</span></span> }, paramLabel = <span class="string"><span class="delimiter">&quot;</span><span class="content">ARCHIVE</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">the archive file</span><span class="delimiter">&quot;</span></span>)
    <span class="predefined-type">File</span> archive;

    <span class="annotation">@Parameters</span>(paramLabel = <span class="string"><span class="delimiter">&quot;</span><span class="content">FILE</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">one or more files to archive</span><span class="delimiter">&quot;</span></span>)
    <span class="predefined-type">File</span><span class="type">[]</span> files;

    <span class="annotation">@Option</span>(names = { <span class="string"><span class="delimiter">&quot;</span><span class="content">-h</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--help</span><span class="delimiter">&quot;</span></span> }, usageHelp = <span class="predefined-constant">true</span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">display a help message</span><span class="delimiter">&quot;</span></span>)
    <span class="directive">private</span> <span class="type">boolean</span> helpRequested;
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>Picocli matches the option names to set the field values.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="predefined-type">String</span><span class="type">[]</span> args = { <span class="string"><span class="delimiter">&quot;</span><span class="content">-c</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--file</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">result.tar</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">file1.txt</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">file2.txt</span><span class="delimiter">&quot;</span></span> };
Tar tar = <span class="keyword">new</span> Tar();
<span class="keyword">new</span> CommandLine(tar).parse(args);

<span class="keyword">assert</span> !tar.helpRequested;
<span class="keyword">assert</span>  tar.create;
<span class="keyword">assert</span>  tar.archive.equals(<span class="keyword">new</span> <span class="predefined-type">File</span>(<span class="string"><span class="delimiter">&quot;</span><span class="content">result.tar</span><span class="delimiter">&quot;</span></span>));
<span class="keyword">assert</span>  <span class="predefined-type">Arrays</span>.equals(tar.files, <span class="keyword">new</span> <span class="predefined-type">File</span><span class="type">[]</span> {<span class="keyword">new</span> <span class="predefined-type">File</span>(<span class="string"><span class="delimiter">&quot;</span><span class="content">file1.txt</span><span class="delimiter">&quot;</span></span>), <span class="keyword">new</span> <span class="predefined-type">File</span>(<span class="string"><span class="delimiter">&quot;</span><span class="content">file2.txt</span><span class="delimiter">&quot;</span></span>)});</code></pre>
</div>
</div>
<div class="paragraph">
<p>Picocli supports <a href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html#tag_12_02">POSIX clustered short options</a>:
one or more single-character options without option-arguments, followed by at most one option with an option-argument, can be grouped behind one &#8216;-&#8217; dash.</p>
</div>
<div class="paragraph">
<p>For example, for the <code>Tar</code> example above, the following command line invocations are equivalent:</p>
</div>
<div class="listingblock">
<div class="title">Example commands with clustered short options</div>
<div class="content">
<pre>tar -c -f result.tar f1.txt f2.txt
tar -cf result.tar f1.txt f2.txt
tar -cfresult.tar f1.txt f2.txt</pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_interactive_password_options">3.2. Interactive (Password) Options</h3>
<div class="paragraph">
<p>For options and positional parameters marked as <code>interactive</code>, the user is prompted to enter a value on the console.
When running on Java 6 or higher, picocli will use the <a href="https://docs.oracle.com/javase/8/docs/api/java/io/Console.html#readPassword-java.lang.String-java.lang.Object&#8230;&#8203;-"><code>Console.readPassword</code></a> API so that user input is not echoed to the console.</p>
</div>
<div class="paragraph">
<p>The user manual has an <a href="http://picocli.info/#_interactive_password_options">example</a>.</p>
</div>
</div>
<div class="sect2">
<h3 id="_positional_parameters">3.3. Positional Parameters</h3>
<div class="paragraph">
<p>Any command line arguments that are not subcommands, options or option parameters are interpreted as positional parameters.</p>
</div>
<div class="paragraph">
<p>Use the (zero-based) <code>index</code> attribute to specify exactly which parameters to capture.
Omitting the <code>index</code> attribute means the field captures <em>all</em> positional parameters.
Array or collection fields can capture multiple values.</p>
</div>
<div class="paragraph">
<p>The <code>index</code> attribute accepts <em>range</em> values, so an annotation like <code>@Parameters(index = "2..4")</code> captures the arguments at index 2, 3 and 4. Range values can be <em>open-ended</em>. For example, <code>@Parameters(index = "3..*")</code> captures all arguments from index 3 and up.</p>
</div>
<div class="paragraph">
<p>For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="type">class</span> <span class="class">PositionalDemo</span> {
    <span class="annotation">@Parameters</span>(index = <span class="string"><span class="delimiter">&quot;</span><span class="content">0</span><span class="delimiter">&quot;</span></span>)    <span class="predefined-type">InetAddress</span> host;
    <span class="annotation">@Parameters</span>(index = <span class="string"><span class="delimiter">&quot;</span><span class="content">1</span><span class="delimiter">&quot;</span></span>)    <span class="type">int</span> port;
    <span class="annotation">@Parameters</span>(index = <span class="string"><span class="delimiter">&quot;</span><span class="content">2..*</span><span class="delimiter">&quot;</span></span>) <span class="predefined-type">List</span>&lt;<span class="predefined-type">File</span>&gt; files;
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>Picocli initializes fields with the values at the specified index in the arguments array.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="predefined-type">String</span><span class="type">[]</span> args = { <span class="string"><span class="delimiter">&quot;</span><span class="content">localhost</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">12345</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">file1.txt</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">file2.txt</span><span class="delimiter">&quot;</span></span> };
PositionalDemo params = CommandLine.populateCommand(<span class="keyword">new</span> PositionalDemo(), args);

<span class="keyword">assert</span> params.host.getHostName().equals(<span class="string"><span class="delimiter">&quot;</span><span class="content">localhost</span><span class="delimiter">&quot;</span></span>);
<span class="keyword">assert</span> params.port == <span class="integer">12345</span>;
<span class="keyword">assert</span> params.files.equals(<span class="predefined-type">Arrays</span>.asList(<span class="keyword">new</span> <span class="predefined-type">File</span>(<span class="string"><span class="delimiter">&quot;</span><span class="content">file1.txt</span><span class="delimiter">&quot;</span></span>), <span class="keyword">new</span> <span class="predefined-type">File</span>(<span class="string"><span class="delimiter">&quot;</span><span class="content">file2.txt</span><span class="delimiter">&quot;</span></span>)));</code></pre>
</div>
</div>
<div class="paragraph">
<p>The user manual has more details about options and positional parameters, as well as the <code>--</code> <a href="http://picocli.info/#_double_dash_code_code">end-of-options delimiter</a> and parameter files (<a href="http://picocli.info/#AtFiles"><code>@</code>-files</a>).</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_strongly_typed_everything">4. Strongly Typed Everything</h2>
<div class="sectionbody">
<div class="paragraph">
<p>When command line options and positional parameters are mapped to the annotated fields,
the text value is converted to the type of the annotated field.</p>
</div>
<div class="sect2">
<h3 id="_type_conversion">4.1. Type Conversion</h3>
<div class="paragraph">
<p>Out of the box, picocli can convert command line argument strings to a number of common data types.</p>
</div>
<div class="paragraph">
<p>See the user manual for the full list of <a href="http://picocli.info/#_built_in_types">built-in types</a>, but in general all primitive types and their Object equivalent,
any enum, and common classes like <code>File</code>, <code>Date</code>, <code>URL</code>, <code>BigDecimal</code>, regex <code>Pattern</code> etc. can be used as is.
Applications running on Java 7 can use <code>Path</code>, and on Java 8 the new <code>java.time</code> classes can be used.</p>
</div>
<div class="paragraph">
<p>You can also use a <a href="http://picocli.info/#_custom_type_converters">custom type converter</a> to handle data types other than the above built-in ones.</p>
</div>
</div>
<div class="sect2">
<h3 id="_collections_and_maps">4.2. Collections and Maps</h3>
<div class="paragraph">
<p>If an option or positional parameter can have multiple values, the field type must be an array, a <code>Collection</code> or a <code>Map</code>.
Any <code>Collection</code> subclass like <code>List</code>, <code>Set</code>, or <code>Queue</code> can be used.</p>
</div>
<div class="paragraph">
<p>A common requirement is to have options with key-value pairs similar to Java&#8217;s system properties, like <code>-Dkey=value</code>.
To achieve this, all you need to do is use a <code>Map</code> field.</p>
</div>
<div class="paragraph">
<p><code>Map</code> fields may have any type for their key and value
as long as a <a href="#_strongly_typed_everything">type converter</a> is registered for both the key and the value type.
Key and value types are inferred from the map&#8217;s generic type parameters.
For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="type">class</span> <span class="class">MapDemo</span> {
    <span class="annotation">@Option</span>(names = {<span class="string"><span class="delimiter">&quot;</span><span class="content">-u</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--timeUnit</span><span class="delimiter">&quot;</span></span>});
    <span class="predefined-type">Map</span>&lt;java.util.concurrent.TimeUnit, <span class="predefined-type">Long</span>&gt; timeout;
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>The following command line would result in four key-value entries in the map:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="bash">&lt;command&gt; -uDAYS=3 -u HOURS=23 -u=MINUTES=59 --timeUnit=SECONDS=13</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_required_arguments">5. Required Arguments</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_required_options">5.1. Required Options</h3>
<div class="paragraph">
<p>Options can be marked <code>required</code> to make it mandatory for the user to specify them on the command line. When a required option is not specified, a <code>MissingParameterException</code> is thrown from the <code>parse</code> method. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-n</span><span class="delimiter">&quot;</span></span>, required = <span class="predefined-constant">true</span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">mandatory number</span><span class="delimiter">&quot;</span></span>)
<span class="type">int</span> number;</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_required_parameters">5.2. Required Parameters</h3>
<div class="paragraph">
<p>Use the <code>arity</code> attribute to make <code>@Parameters</code> mandatory:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Parameters</span>(arity = <span class="string"><span class="delimiter">&quot;</span><span class="content">1..*</span><span class="delimiter">&quot;</span></span>, descriptions = <span class="string"><span class="delimiter">&quot;</span><span class="content">at least one File</span><span class="delimiter">&quot;</span></span>)
<span class="predefined-type">List</span>&lt;<span class="predefined-type">File</span>&gt; files;</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_multiple_values">6. Multiple Values</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Multi-valued options and positional parameters are annotated fields that can capture multiple values from the command line.</p>
</div>
<div class="sect2">
<h3 id="_repeated_options">6.1. Repeated Options</h3>
<div class="paragraph">
<p>The simplest way to create a multi-valued option is to declare an annotated field whose type is an array, collection or a map.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-option</span><span class="delimiter">&quot;</span></span>)
<span class="type">int</span><span class="type">[]</span> values;</code></pre>
</div>
</div>
<div class="paragraph">
<p>Users may specify the same option multiple times. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>&lt;command&gt; -option 111 -option 222 -option 333</pre>
</div>
</div>
<div class="paragraph">
<p>Each value is appended to the array or collection.</p>
</div>
</div>
<div class="sect2">
<h3 id="_split_regex">6.2. Split Regex</h3>
<div class="paragraph">
<p>Options and parameters may also specify a <code>split</code> regular expression used to split each option parameter into smaller substrings.
Each of these substrings is converted to the type of the collection or array. See <a href="#_collections_and_maps">Collections and Maps</a>.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-option</span><span class="delimiter">&quot;</span></span>, split = <span class="string"><span class="delimiter">&quot;</span><span class="content">,</span><span class="delimiter">&quot;</span></span>)
<span class="type">int</span><span class="type">[]</span> values;</code></pre>
</div>
</div>
<div class="paragraph">
<p>A single command line argument like the following will be split up and three <code>int</code> values are added to the array:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>-option 111,222,333</pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_arity">6.3. Arity</h3>
<div class="paragraph">
<p>Sometimes you want to define an option that requires more than one option parameter <em>for each option occurrence</em> on the command line.</p>
</div>
<div class="paragraph">
<p>The <code>arity</code> attribute lets you control exactly how many parameters to consume for each option occurrence.</p>
</div>
<div class="paragraph">
<p>The <code>arity</code> attribute can specify an exact number of required parameters, or a <em>range</em> with a minimum and a maximum number of parameters.
The maximum can be an exact upper bound, or it can be <code>"*"</code> to denote <em>any number</em> of parameters. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="type">class</span> <span class="class">ArityDemo</span> {
    <span class="annotation">@Parameters</span>(arity = <span class="string"><span class="delimiter">&quot;</span><span class="content">1..3</span><span class="delimiter">&quot;</span></span>, descriptions = <span class="string"><span class="delimiter">&quot;</span><span class="content">one to three Files</span><span class="delimiter">&quot;</span></span>)
    <span class="predefined-type">File</span><span class="type">[]</span> files;

    <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-f</span><span class="delimiter">&quot;</span></span>, arity = <span class="string"><span class="delimiter">&quot;</span><span class="content">2</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">exactly two floating point numbers</span><span class="delimiter">&quot;</span></span>)
    <span class="type">double</span><span class="type">[]</span> doubles;

    <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-s</span><span class="delimiter">&quot;</span></span>, arity = <span class="string"><span class="delimiter">&quot;</span><span class="content">1..*</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">at least one string</span><span class="delimiter">&quot;</span></span>)
    <span class="predefined-type">String</span><span class="type">[]</span> strings;
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>A <code>MissingParameterException</code> is thrown when fewer than the miminum number of parameters is specified on the command line.</p>
</div>
<div class="sect3">
<h4 id="_default_arity">6.3.1. Default Arity</h4>
<div class="paragraph">
<p>If no <code>arity</code> is specified, the number of parameters depends on the field&#8217;s type.
The user manual has more details on <a href="http://picocli.info/#_default_arity">arity</a>.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_help_options">7. Help Options</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_mixin_standard_help_options">7.1. Mixin Standard Help Options</h3>
<div class="paragraph">
<p>When the <code>mixinStandardHelpOptions</code> command attribute is set to <code>true</code>, picocli adds a <a href="#_reuse">mixin</a> to the
command that adds <a href="#_custom_help_options"><code>usageHelp</code></a> and <a href="#_custom_help_options"><code>versionHelp</code></a> options to the command. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(mixinStandardHelpOptions = <span class="predefined-constant">true</span>, version = <span class="string"><span class="delimiter">&quot;</span><span class="content">auto help demo - picocli 3.0</span><span class="delimiter">&quot;</span></span>)
<span class="type">class</span> <span class="class">AutoHelpDemo</span> <span class="directive">implements</span> <span class="predefined-type">Runnable</span> {

    <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">--option</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Some option.</span><span class="delimiter">&quot;</span></span>)
    <span class="predefined-type">String</span> option;

    <span class="annotation">@Override</span> <span class="directive">public</span> <span class="type">void</span> run() { ... }
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>The usage help message for the above example looks like this:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: &lt;main class&gt; [-hV] [--option=&lt;option&gt;]
      --option=&lt;option&gt;   Some option.
  -h, --help              Show this help message and exit.
  -V, --version           Print version information and exit.</pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_custom_help_options">7.2. Custom Help Options</h3>
<div class="paragraph">
<p>Applications can define custom help options by setting attribute <code>versionHelp = true</code>, <code>usageHelp = true</code> or <code>help = true</code>.
If one of the arguments specified on the command line is a "help" option, picocli will not throw a <code>MissingParameterException</code> when required options are missing.</p>
</div>
<div class="paragraph">
<p>For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Option</span>(names = {<span class="string"><span class="delimiter">&quot;</span><span class="content">-V</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--version</span><span class="delimiter">&quot;</span></span>}, versionHelp = <span class="predefined-constant">true</span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">display version info</span><span class="delimiter">&quot;</span></span>)
<span class="type">boolean</span> versionInfoRequested;

<span class="annotation">@Option</span>(names = {<span class="string"><span class="delimiter">&quot;</span><span class="content">?</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">-h</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--help</span><span class="delimiter">&quot;</span></span>}, usageHelp = <span class="predefined-constant">true</span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">display this help message</span><span class="delimiter">&quot;</span></span>)
<span class="type">boolean</span> usageHelpRequested;</code></pre>
</div>
</div>
<div class="paragraph">
<p>Use these attributes for options that request the usage help message or version information to be shown on the console.</p>
</div>
<div class="paragraph">
<p>The <code>CommandLine</code> class offers two methods that allow external components to detect whether
usage help or version information was requested (without inspecting the annotated domain object):</p>
</div>
<div class="ulist">
<ul>
<li>
<p><code>CommandLine.isUsageHelpRequested()</code> returns <code>true</code> if the parser matched an option annotated with <code>usageHelp=true</code></p>
</li>
<li>
<p><code>CommandLine.isVersionHelpRequested()</code> returns <code>true</code> if the parser matched an option annotated with <code>versionHelp=true</code></p>
</li>
</ul>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java">CommandLine commandLine = <span class="keyword">new</span> CommandLine(<span class="keyword">new</span> App());
commandLine.parse(args);
<span class="keyword">if</span> (commandLine.isUsageHelpRequested()) {
   commandLine.usage(<span class="predefined-type">System</span>.out);
   <span class="keyword">return</span>;
} <span class="keyword">else</span> <span class="keyword">if</span> (commandLine.isVersionHelpRequested()) {
   commandLine.printVersionHelp(<span class="predefined-type">System</span>.out);
   <span class="keyword">return</span>;
}
<span class="comment">// ... run App's business logic</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>See also <a href="#_parsing">Parsing</a> and <a href="#_runnable_and_callable">Runnable and Callable</a> for how picocli can help reduce boilerplate code.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_version_help">8. Version Help</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_static_version_information">8.1. Static Version Information</h3>
<div class="paragraph">
<p>Applications can specify version information in the <code>version</code> attribute of the <code>@Command</code> annotation.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(version = <span class="string"><span class="delimiter">&quot;</span><span class="content">1.0</span><span class="delimiter">&quot;</span></span>)
<span class="type">class</span> <span class="class">VersionedCommand</span> { ... }</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>CommandLine.printVersionHelp(PrintStream)</code> method extracts the version information from this
annotation and prints it to the specified <code>PrintStream</code>.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java">CommandLine commandLine = <span class="keyword">new</span> CommandLine(<span class="keyword">new</span> VersionedCommand());
<span class="comment">//...</span>
commandLine.printVersionHelp(<span class="predefined-type">System</span>.out);</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>version</code> may specify multiple Strings, and may contain <a href="#_usage_help_with_styles_and_colors">markup</a> to show ANSI styles and colors. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(version = {
        <span class="string"><span class="delimiter">&quot;</span><span class="content">@|yellow Versioned Command 1.0|@</span><span class="delimiter">&quot;</span></span>,
        <span class="string"><span class="delimiter">&quot;</span><span class="content">@|blue Build 12345|@</span><span class="delimiter">&quot;</span></span>,
        <span class="string"><span class="delimiter">&quot;</span><span class="content">@|red,bg(white) (c) 2017|@</span><span class="delimiter">&quot;</span></span> })
<span class="type">class</span> <span class="class">VersionedCommand</span> { ... }</code></pre>
</div>
</div>
<div class="paragraph">
<p>The markup will be rendered as ANSI escape codes on supported systems.</p>
</div>
<div class="paragraph">
<p><span class="image"><img src="images/VersionInfoWithColors.png" alt="Screenshot of version information containing markup with Ansi styles and colors"></span></p>
</div>
</div>
<div class="sect2">
<h3 id="_dynamic_version_information">8.2. Dynamic Version Information</h3>
<div class="paragraph">
<p>The <code>@Command</code> annotation supports a <code>versionProvider</code> attribute.
Applications may specify a <code>IVersionProvider</code> implementation in this attribute, and picocli will instantiate this class
and invoke it to collect version information.</p>
</div>
<div class="paragraph">
<p>The GitHub project has an
<a href="https://github.com/remkop/picocli/blob/master/picocli-examples/src/main/java/picocli/examples/VersionProviderDemo2.java">example</a>
implementation that gets the version from the manifest file and another
<a href="https://github.com/remkop/picocli/blob/master/picocli-examples/src/main/java/picocli/examples/VersionProviderDemo1.java">example</a>
that gets version information from a build-generated version properties file.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_usage_help">9. Usage Help</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_example_usage_message">9.1. Example Usage Message</h3>
<div class="paragraph">
<p>Picocli makes it easy for your application to generate a usage help message like this:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: cat [-AbeEnstTuv] [--help] [--version] [FILE...]
Concatenate FILE(s), or standard input, to standard output.
      FILE                 Files whose contents to display
  -A, --show-all           equivalent to -vET
  -b, --number-nonblank    number nonempty output lines, overrides -n
  -e                       equivalent to -vET
  -E, --show-ends          display $ at end of each line
  -n, --number             number all output lines
  -s, --squeeze-blank      suppress repeated empty output lines
  -t                       equivalent to -vT
  -T, --show-tabs          display TAB characters as ^I
  -u                       (ignored)
  -v, --show-nonprinting   use ^ and M- notation, except for LDF and TAB
      --help               display this help and exit
      --version            output version information and exit
Copyright(c) 2017</pre>
</div>
</div>
<div class="paragraph">
<p>The usage help message is generated from annotation attributes, like below:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(name = <span class="string"><span class="delimiter">&quot;</span><span class="content">cat</span><span class="delimiter">&quot;</span></span>, footer = <span class="string"><span class="delimiter">&quot;</span><span class="content">Copyright(c) 2017</span><span class="delimiter">&quot;</span></span>,
         description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Concatenate FILE(s), or standard input, to standard output.</span><span class="delimiter">&quot;</span></span>)
<span class="type">class</span> <span class="class">Cat</span> {

  <span class="annotation">@Parameters</span>(paramLabel = <span class="string"><span class="delimiter">&quot;</span><span class="content">FILE</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Files whose contents to display</span><span class="delimiter">&quot;</span></span>)
  <span class="predefined-type">List</span>&lt;<span class="predefined-type">File</span>&gt; files;

  <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">--help</span><span class="delimiter">&quot;</span></span>, usageHelp = <span class="predefined-constant">true</span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">display this help and exit</span><span class="delimiter">&quot;</span></span>)
  <span class="type">boolean</span> help;

  <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-t</span><span class="delimiter">&quot;</span></span>,                 description = <span class="string"><span class="delimiter">&quot;</span><span class="content">equivalent to -vT</span><span class="delimiter">&quot;</span></span>)  <span class="type">boolean</span> t;
  <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-e</span><span class="delimiter">&quot;</span></span>,                 description = <span class="string"><span class="delimiter">&quot;</span><span class="content">equivalent to -vET</span><span class="delimiter">&quot;</span></span>) <span class="type">boolean</span> e;
  <span class="annotation">@Option</span>(names = {<span class="string"><span class="delimiter">&quot;</span><span class="content">-A</span><span class="delimiter">&quot;</span></span>, <span class="string"><span class="delimiter">&quot;</span><span class="content">--show-all</span><span class="delimiter">&quot;</span></span>}, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">equivalent to -vET</span><span class="delimiter">&quot;</span></span>) <span class="type">boolean</span> all;

  <span class="comment">// ...</span>
}</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_usage_help_message_elements">9.2. Usage Help Message Elements</h3>
<div class="paragraph">
<p>The various elements of the usage help message are easily customized with annotations.</p>
</div>
<div class="sect3">
<h4 id="_command_name">9.2.1. Command Name</h4>
<div class="paragraph">
<p>In the above example, the program name is taken from the <code>name</code> attribute of the <code>Command</code> annotation:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(name = <span class="string"><span class="delimiter">&quot;</span><span class="content">cat</span><span class="delimiter">&quot;</span></span>)</code></pre>
</div>
</div>
<div class="paragraph">
<p>Without a <code>name</code> attribute, picocli will show a generic <code>&lt;main class&gt;</code> in the synopsis:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: &lt;main class&gt; [-AbeEnstTuv] [--help] [--version] [FILE...]</pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_parameter_labels">9.2.2. Parameter Labels</h4>
<div class="paragraph">
<p>Non-boolean options require a value. The usage help should explain this, and picocli shows the option parameter
in the synopsis and in the option list. By default, the field name is shown in <code>&lt;</code> and <code>&gt;</code> fish brackets.
Use the <code>paramLabel</code> attribute to display a different name. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: &lt;main class&gt; [-f=FILE] [-n=&lt;number&gt;] NUM &lt;host&gt;
      NUM        number param
      host       the host
  -f= FILE       a file
  -n= &lt;number&gt;   number option</pre>
</div>
</div>
<div class="paragraph">
<p>Some annotated fields in the below example class have a <code>paramLabel</code> attribute and others don&#8217;t:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>()
<span class="type">class</span> <span class="class">ParamLabels</span> {
    <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-f</span><span class="delimiter">&quot;</span></span>,    description = <span class="string"><span class="delimiter">&quot;</span><span class="content">a file</span><span class="delimiter">&quot;</span></span>,       paramLabel = <span class="string"><span class="delimiter">&quot;</span><span class="content">FILE</span><span class="delimiter">&quot;</span></span>) <span class="predefined-type">File</span> f;
    <span class="annotation">@Option</span>(names = <span class="string"><span class="delimiter">&quot;</span><span class="content">-n</span><span class="delimiter">&quot;</span></span>,    description = <span class="string"><span class="delimiter">&quot;</span><span class="content">number option</span><span class="delimiter">&quot;</span></span>)                     <span class="type">int</span> number;
    <span class="annotation">@Parameters</span>(index = <span class="string"><span class="delimiter">&quot;</span><span class="content">0</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">number param</span><span class="delimiter">&quot;</span></span>, paramLabel = <span class="string"><span class="delimiter">&quot;</span><span class="content">NUM</span><span class="delimiter">&quot;</span></span>)  <span class="type">int</span> n;
    <span class="annotation">@Parameters</span>(index = <span class="string"><span class="delimiter">&quot;</span><span class="content">1</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">the host</span><span class="delimiter">&quot;</span></span>)                          <span class="predefined-type">InetAddress</span> host;
}</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_unsorted_option_list">9.2.3. Unsorted Option List</h4>
<div class="paragraph">
<p>By default the options list displays options in alphabetical order. Use the <code>sortOptions = false</code> attribute to display options in the order they are declared in your class.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(sortOptions = <span class="predefined-constant">false</span>)</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_abbreviated_synopsis">9.2.4. Abbreviated Synopsis</h4>
<div class="paragraph">
<p>If a command is very complex and has many options, it is sometimes desirable to suppress details from the synopsis with the <code>abbreviateSynopsis</code> attribute. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(abbreviateSynopsis = <span class="predefined-constant">true</span>)
<span class="type">class</span> <span class="class">App</span> { ... }</code></pre>
</div>
</div>
<div class="paragraph">
<p>This shows the below synopsis.
Positional parameters are not abbreviated.</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: &lt;main class&gt; [OPTIONS] [&lt;files&gt;...]</pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_custom_synopsis">9.2.5. Custom Synopsis</h4>
<div class="paragraph">
<p>For even more control of the synopsis, use the <code>customSynopsis</code> attribute to specify one or more synopsis lines. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: ln [OPTION]... [-T] TARGET LINK_NAME   (1st form)
  or:  ln [OPTION]... TARGET                  (2nd form)
  or:  ln [OPTION]... TARGET... DIRECTORY     (3rd form)
  or:  ln [OPTION]... -t DIRECTORY TARGET...  (4th form)</pre>
</div>
</div>
<div class="paragraph">
<p>To produce a synopsis like the above, specify the literal text in the <code>customSynopsis</code> attribute:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(synopsisHeading = <span class="string"><span class="delimiter">&quot;</span><span class="delimiter">&quot;</span></span>, customSynopsis = {
        <span class="string"><span class="delimiter">&quot;</span><span class="content">Usage: ln [OPTION]... [-T] TARGET LINK_NAME   (1st form)</span><span class="delimiter">&quot;</span></span>,
        <span class="string"><span class="delimiter">&quot;</span><span class="content">  or:  ln [OPTION]... TARGET                  (2nd form)</span><span class="delimiter">&quot;</span></span>,
        <span class="string"><span class="delimiter">&quot;</span><span class="content">  or:  ln [OPTION]... TARGET... DIRECTORY     (3rd form)</span><span class="delimiter">&quot;</span></span>,
        <span class="string"><span class="delimiter">&quot;</span><span class="content">  or:  ln [OPTION]... -t DIRECTORY TARGET...  (4th form)</span><span class="delimiter">&quot;</span></span>,
})
<span class="type">class</span> <span class="class">Ln</span> { ... }</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_header_and_footer">9.2.6. Header and Footer</h4>
<div class="paragraph">
<p>The <code>header</code> will be shown at the top of the usage help message (before the synopsis). The first header line is also the line shown in the subcommand list if your command has subcommands (see <a href="#_usage_help_for_subcommands">Usage Help for Subcommands</a>).</p>
</div>
<div class="paragraph">
<p>Use the <code>footer</code> attribute to specify one or more lines to show below the generated usage help message.
Each element of the attribute String array is displayed on a separate line.</p>
</div>
<div class="paragraph">
<p>The <code>headerHeading</code> and <code>footerHeading</code> may contain format specifiers. See <a href="#_section_headings">Section Headings</a>.</p>
</div>
</div>
<div class="sect3">
<h4 id="_section_headings">9.2.7. Section Headings</h4>
<div class="paragraph">
<p>Section headers can be used to make usage message layout appear more spacious. Section headings may contain embedded line separator (<code>%n</code>) format specifiers:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(name = <span class="string"><span class="delimiter">&quot;</span><span class="content">commit</span><span class="delimiter">&quot;</span></span>,
        sortOptions = <span class="predefined-constant">false</span>,
        headerHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">Usage:%n%n</span><span class="delimiter">&quot;</span></span>,
        synopsisHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%n</span><span class="delimiter">&quot;</span></span>,
        descriptionHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%nDescription:%n%n</span><span class="delimiter">&quot;</span></span>,
        parameterListHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%nParameters:%n</span><span class="delimiter">&quot;</span></span>,
        optionListHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%nOptions:%n</span><span class="delimiter">&quot;</span></span>,
        header = <span class="string"><span class="delimiter">&quot;</span><span class="content">Record changes to the repository.</span><span class="delimiter">&quot;</span></span>,
        description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Stores the current contents of the index in a new commit </span><span class="delimiter">&quot;</span></span> +
                <span class="string"><span class="delimiter">&quot;</span><span class="content">along with a log message from the user describing the changes.</span><span class="delimiter">&quot;</span></span>)
<span class="type">class</span> <span class="class">GitCommit</span> { ... }</code></pre>
</div>
</div>
<div class="paragraph">
<p>The usage help message generated from this class is shown below in <a href="https://picocli.info/#_expanded_example">Expanded Example</a> in the user manual.</p>
</div>
</div>
<div class="sect3">
<h4 id="_option_parameter_separators">9.2.8. Option-Parameter Separators</h4>
<div class="paragraph">
<p>The separator displayed between options and option parameters (<code>=</code> by default)
in the synopsis and the option list can be configured with the <code>separator</code> attribute.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(separator = <span class="string"><span class="delimiter">&quot;</span><span class="content">:</span><span class="delimiter">&quot;</span></span>)</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_hidden_options_and_parameters">9.2.9. Hidden Options and Parameters</h4>
<div class="paragraph">
<p>Options and Parameters with the <code>hidden</code> attribute set to <code>true</code> will not be shown in the usage help message.
See the <a href="https://picocli.info/#_hidden_options_and_parameters">user manual</a> for details.</p>
</div>
</div>
<div class="sect3">
<h4 id="_show_default_values">9.2.10. Show Default Values</h4>
<div class="paragraph">
<p>The <a href="http://picocli.info/#_default_values">default value</a> for an option or positional parameter
can be embedded in the description by specifying the variable <code>${DEFAULT-VALUE}</code> in the description text.
See the <a href="https://picocli.info/#_show_default_values">user manual</a> for details.</p>
</div>
<div class="paragraph">
<p>Similarly, it is possible to embed the completion candidates in the description for an option or positional parameter by
specifying the variable <code>${COMPLETION-CANDIDATES}</code> in the description text.
See the <a href="https://picocli.info/#_show_default_values">user manual</a> for details.</p>
</div>
</div>
<div class="sect3">
<h4 id="_required_option_marker">9.2.11. Required-Option Marker</h4>
<div class="paragraph">
<p>Required options can be marked in the option list by the character specified with the <code>requiredOptionMarker</code> attribute.
See the <a href="https://picocli.info/#_required_option_marker">user manual</a> for details.</p>
</div>
</div>
<div class="sect3">
<h4 id="_usage_width">9.2.12. Usage Width</h4>
<div class="paragraph">
<p>The default width of the usage help message is 80 characters.
System property <code>picocli.usage.width</code> can be used to specify a custom width.
The minimum width that can be configured is 55 characters.</p>
</div>
<div class="paragraph">
<p>The width can also be set programmatically via the <code>CommandLine::setUsageHelpWidth</code> and <code>UsageMessageSpec::width</code> methods.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_ansi_colors_and_styles">10. ANSI Colors and Styles</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_colorized_example">10.1. Colorized Example</h3>
<div class="paragraph">
<p>Below shows the same usage help message as shown in the <a href="https://picocli.info/#_expanded_example">Expanded Example</a> in the user manual, with ANSI escape codes enabled.</p>
</div>
<div class="paragraph">
<p><span class="image"><img src="images/UsageHelpWithStyle.png" alt="Screenshot of usage help with Ansi codes enabled"></span></p>
</div>
</div>
<div class="sect2">
<h3 id="_usage_help_with_styles_and_colors">10.2. Usage Help with Styles and Colors</h3>
<div class="paragraph">
<p>You can use colors and styles in the descriptions, header and footer
of the usage help message.</p>
</div>
<div class="paragraph">
<p>Picocli supports a custom markup notation for mixing colors and styles in text,
following a convention introduced by <a href="https://github.com/fusesource/jansi">Jansi</a>, where
<code>@|</code> starts a styled section, and <code>|@</code> ends it.
Immediately following the <code>@|</code> is a comma-separated list of colors and styles, so <code>@|STYLE1[,STYLE2]&#8230;&#8203; text|@</code>.
For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Custom @|bold,underline styles|@ and @|fg(red) colors|@.</span><span class="delimiter">&quot;</span></span>)</code></pre>
</div>
</div>
<div class="paragraph">
<p><span class="image"><img src="images/DescriptionWithColors.png" alt="Description with Ansi styles and colors"></span></p>
</div>
<table class="tableblock frame-all grid-cols spread">
<caption class="title">Table 1. Pre-defined styles and colors that can be used in descriptions and headers using the <code>@|STYLE1[,STYLE2]&#8230;&#8203; text|@</code> notation</caption>
<colgroup>
<col style="width: 50%;">
<col style="width: 50%;">
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">Pre-defined Styles</th>
<th class="tableblock halign-left valign-top">Pre-defined Colors</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">bold</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">black</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">faint</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">red</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">underline</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">green</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">italic</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">yellow</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">blink</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">blue</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">reverse</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">magenta</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">reset</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">cyan</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">white</p></td>
</tr>
</tbody>
</table>
<div class="paragraph">
<p>Colors are applied as <em>foreground</em> colors by default.
You can set <em>background</em> colors by specifying <code>bg(&lt;color&gt;)</code>.
For example, <code>@|bg(red) text with red background|@</code>.
Similarly, <code>fg(&lt;color&gt;)</code> explicitly sets the foreground color.</p>
</div>
<div class="paragraph">
<p>The example below shows how this markup can be used to add colors and styles to the headings and descriptions of a usage help message:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(name = <span class="string"><span class="delimiter">&quot;</span><span class="content">commit</span><span class="delimiter">&quot;</span></span>,
        sortOptions = <span class="predefined-constant">false</span>,
        headerHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">@|bold,underline Usage|@:%n%n</span><span class="delimiter">&quot;</span></span>,
        synopsisHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%n</span><span class="delimiter">&quot;</span></span>,
        descriptionHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%n@|bold,underline Description|@:%n%n</span><span class="delimiter">&quot;</span></span>,
        parameterListHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%n@|bold,underline Parameters|@:%n</span><span class="delimiter">&quot;</span></span>,
        optionListHeading = <span class="string"><span class="delimiter">&quot;</span><span class="content">%n@|bold,underline Options|@:%n</span><span class="delimiter">&quot;</span></span>,
        header = <span class="string"><span class="delimiter">&quot;</span><span class="content">Record changes to the repository.</span><span class="delimiter">&quot;</span></span>,
        description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Stores the current contents of the index in a new commit </span><span class="delimiter">&quot;</span></span> +
                <span class="string"><span class="delimiter">&quot;</span><span class="content">along with a log message from the user describing the changes.</span><span class="delimiter">&quot;</span></span>)
<span class="type">class</span> <span class="class">GitCommit</span> { ... }</code></pre>
</div>
</div>
<div class="admonitionblock caution">
<table>
<tr>
<td class="icon">
<i class="fa icon-caution" title="Caution"></i>
</td>
<td class="content">
Markup styles cannot be nested, for example: <code>@|bold this @|underline that|@|@</code> will not work. You can achieve the same by combining styles, for example: <code>@|bold this|@ @|bold,underline that|@</code> will work fine.
</td>
</tr>
</table>
</div>
<div class="sect3">
<h4 id="_more_colors">10.2.1. More Colors</h4>
<div class="paragraph">
<p>There are only eight pre-defined named colors, but most terminals support a 256 color indexed palette.</p>
</div>
<div class="paragraph">
<p>See the  <a href="https://picocli.info/#_more_colors">More Colors</a> section of the user manual for using these colors as foreground or background colors.</p>
</div>
<div class="paragraph">
<p><span class="image"><img src="images/256colors.png" alt="256 color indexed palette"></span></p>
</div>
</div>
<div class="sect3">
<h4 id="_color_scheme_for_fixed_elements">10.2.2. Color Scheme for Fixed Elements</h4>
<div class="paragraph">
<p>Picocli uses a default color scheme for options, parameters and commands.
There are no annotations to modify this color scheme, but it can be changed programmatically and with system properties.
For details, see the <a href="https://picocli.info/#_configuring_fixed_elements">Color Scheme</a> section of the user manual.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_supported_platforms">10.3. Supported Platforms</h3>
<div class="paragraph">
<p>Picocli will only emit ANSI escape codes on supported platforms.
This includes most Unix and Linux platforms.
See the <a href="https://picocli.info/#_supported_platforms">Windows</a> section of the user manual for the various options available to add coloring support to the Windows command console.</p>
</div>
</div>
<div class="sect2">
<h3 id="_forcing_ansi_on_off">10.4. Forcing ANSI On/Off</h3>
<div class="paragraph">
<p>You can force picocli to either always use ANSI codes or never use ANSI codes regardless of the platform:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Setting system property <code>picocli.ansi</code> to <code>true</code> forces picocli to use ANSI codes; setting <code>picocli.ansi</code> to <code>false</code> forces picocli to <strong>not</strong> use ANSI codes. This may be a useful facility for users of your command line application.</p>
</li>
<li>
<p>You can decide to force disable or force enable ANSI escape codes programmatically by specifying <code>Ansi.ON</code> or <code>Ansi.OFF</code> when invoking <code>CommandLine.usage</code>.
This overrides the value of system property <code>picocli.ansi</code>. For example:</p>
</li>
</ul>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="keyword">import</span> <span class="include">picocli.CommandLine.Help.Ansi</span>;

App app = CommandLine.usage(<span class="keyword">new</span> App(), <span class="predefined-type">System</span>.out, Ansi.OFF, args);</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_subcommands">11. Subcommands</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_registering_subcommands">11.1. Registering Subcommands</h3>
<div class="paragraph">
<p>Subcommands can be registered programmatically or declaratively</p>
</div>
<div class="sect3">
<h4 id="_programmatically">11.1.1. Programmatically</h4>
<div class="paragraph">
<p>Subcommands can be registered with the <code>CommandLine.addSubcommand</code> method.
You pass in the name of the command and the annotated object to populate with the subcommand options.
The specified name is used by the parser to recognize subcommands in the command line arguments.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java">CommandLine commandLine = <span class="keyword">new</span> CommandLine(<span class="keyword">new</span> Git())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">status</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitStatus())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">commit</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitCommit())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">add</span><span class="delimiter">&quot;</span></span>,      <span class="keyword">new</span> GitAdd())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">branch</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitBranch())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">checkout</span><span class="delimiter">&quot;</span></span>, <span class="keyword">new</span> GitCheckout())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">clone</span><span class="delimiter">&quot;</span></span>,    <span class="keyword">new</span> GitClone())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">diff</span><span class="delimiter">&quot;</span></span>,     <span class="keyword">new</span> GitDiff())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">merge</span><span class="delimiter">&quot;</span></span>,    <span class="keyword">new</span> GitMerge())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">push</span><span class="delimiter">&quot;</span></span>,     <span class="keyword">new</span> GitPush())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">rebase</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitRebase())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">tag</span><span class="delimiter">&quot;</span></span>,      <span class="keyword">new</span> GitTag());</code></pre>
</div>
</div>
<div class="admonitionblock caution">
<table>
<tr>
<td class="icon">
<i class="fa icon-caution" title="Caution"></i>
</td>
<td class="content">
<em>Note on custom type converters:</em> custom type converters are registered only with the subcommands and nested
sub-subcommands that were added <em>before</em> the custom type was registered.
To ensure a custom type converter is available to all subcommands, register the type converter last, after
adding subcommands.
</td>
</tr>
</table>
</div>
</div>
<div class="sect3">
<h4 id="_declaratively">11.1.2. Declaratively</h4>
<div class="paragraph">
<p>Subcommands can be registered declaratively with the <code>@Command</code> annotation&#8217;s <code>subcommands</code> attribute.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(name = <span class="string"><span class="delimiter">&quot;</span><span class="content">git</span><span class="delimiter">&quot;</span></span>, subcommands = {
    GitStatus.class,
    GitCommit.class,
    GitAdd.class,
    GitBranch.class,
    GitCheckout.class,
    GitClone.class,
    GitDiff.class,
    GitMerge.class,
    GitPush.class,
    GitRebase.class,
    GitTag.class
})
<span class="directive">public</span> <span class="type">class</span> <span class="class">Git</span> { ... }</code></pre>
</div>
</div>
<div class="paragraph">
<p>The declared subcommands are automatically instantiated and added when the <code>new CommandLine(new Git())</code> instance is constructed.</p>
</div>
<div class="paragraph">
<p>Subcommands referenced in a <code>subcommands</code> attribute <em>must</em> have a <code>@Command</code> annotation with a <code>name</code> attribute, or an exception is thrown from the <code>CommandLine</code> constructor.</p>
</div>
</div>
<div class="sect3">
<h4 id="_nesting_subcommands">11.1.3. Nesting Subcommands</h4>
<div class="paragraph">
<p>Subcommands can be nested to any arbitrary level of depth. See the <a href="https://picocli.info/#_nested_sub_subcommands">Nested sub-Subcommands</a> section of the user manual for details.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_parsing_subcommands">11.2. Parsing Subcommands</h3>
<div class="paragraph">
<p>For this example, we assume we created an alias <code>git</code> that invokes our Java application. This could also be a script or a function that calls our Java program:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="bash">alias git='java picocli.Demo$Git'</code></pre>
</div>
</div>
<div class="paragraph">
<p>Next, we call our command with some arguments like this:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="bash">git --git-dir=/home/rpopma/picocli status -sb -uno</code></pre>
</div>
</div>
<div class="paragraph">
<p>Where <code>git</code> (actually <code>java picocli.Demo$Git</code>) is the top-level command, followed by a global option and a subcommand <code>status</code> with its own options.</p>
</div>
<div class="paragraph">
<p>Setting up the parser and parsing the command line could look like this:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="directive">public</span> <span class="directive">static</span> <span class="type">void</span> main(<span class="predefined-type">String</span>... args) {
    <span class="comment">// Set up the parser</span>
    CommandLine commandLine = <span class="keyword">new</span> CommandLine(<span class="keyword">new</span> Git());

    <span class="comment">// add subcommands programmatically (not necessary if the parent command</span>
    <span class="comment">// declaratively registers the subcommands via annotation)</span>
    commandLine.addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">status</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitStatus())
               .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">commit</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitCommit())
                ...

    <span class="comment">// Invoke the parse method to parse the arguments</span>
    List&lt;CommandLine&gt; parsed = commandLine.parse(args);
    handleParseResult(parsed);
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>CommandLine.parse</code> method returns a List with the recognized commands. The top-level command (the Java class invoked by <code>git</code> in this example) is always the first element in the returned list.</p>
</div>
<div class="paragraph">
<p>The returned List also contains all matched subcommands. Your application needs to inspect this list to see what subcommand was invoked and take appropriate action. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="directive">private</span> <span class="type">void</span> handleParseResult(<span class="predefined-type">List</span>&lt;CommandLine&gt; parsed) {
    <span class="keyword">assert</span> parsed.size() == <span class="integer">2</span> : <span class="string"><span class="delimiter">&quot;</span><span class="content">1 command and 1 subcommand found</span><span class="delimiter">&quot;</span></span>

    <span class="keyword">assert</span> parsed.get(<span class="integer">0</span>).getCommand().getClass() == Git.class       : <span class="string"><span class="delimiter">&quot;</span><span class="content">main command</span><span class="delimiter">&quot;</span></span>
    <span class="keyword">assert</span> parsed.get(<span class="integer">1</span>).getCommand().getClass() == GitStatus.class : <span class="string"><span class="delimiter">&quot;</span><span class="content">subcommand</span><span class="delimiter">&quot;</span></span>

    Git git = (Git) parsed.get(<span class="integer">0</span>).getCommand();
    <span class="keyword">assert</span> git.gitDir.equals(<span class="keyword">new</span> <span class="predefined-type">File</span>(<span class="string"><span class="delimiter">&quot;</span><span class="content">/home/rpopma/picocli</span><span class="delimiter">&quot;</span></span>));

    GitStatus gitstatus = (GitStatus) parsed.get(<span class="integer">1</span>).getCommand();
    <span class="keyword">assert</span>  gitstatus.shortFormat              : <span class="string"><span class="delimiter">&quot;</span><span class="content">git status -s</span><span class="delimiter">&quot;</span></span>
    <span class="keyword">assert</span>  gitstatus.branchInfo               : <span class="string"><span class="delimiter">&quot;</span><span class="content">git status -b</span><span class="delimiter">&quot;</span></span>
    <span class="keyword">assert</span> !gitstatus.showIgnored              : <span class="string"><span class="delimiter">&quot;</span><span class="content">git status --showIgnored not specified</span><span class="delimiter">&quot;</span></span>
    <span class="keyword">assert</span>  gitstatus.mode == GitStatusMode.no : <span class="string"><span class="delimiter">&quot;</span><span class="content">git status -u=no</span><span class="delimiter">&quot;</span></span>
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>You may be interested in the <a href="#_convenience_methods_for_subcommands">convenience methods for subcommands</a> to reduce error handling and other boilerplate code in your application.</p>
</div>
</div>
<div class="sect2">
<h3 id="__code_parentcommand_code_annotation">11.3. <code>@ParentCommand</code> Annotation</h3>
<div class="paragraph">
<p>In command line applications with subcommands, options of the top level command are often intended as "global" options that apply to all the subcommands.
The <code>@ParentCommand</code> annotation makes it easy for subcommands to access their parent command options: subcommand fields annotated with <code>@ParentCommand</code> are initialized with a reference to the parent command.
The user manual has an example showing <a href="https://picocli.info/#__code_parentcommand_code_annotation">how to use the <code>@ParentCommand</code> annotation</a>.</p>
</div>
</div>
<div class="sect2">
<h3 id="_usage_help_for_subcommands">11.4. Usage Help for Subcommands</h3>
<div class="paragraph">
<p>After registering subcommands, calling the <code>commandLine.usage</code> method will show a usage help message that includes all subcommands in the order they were registered. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>Usage: git [-hV] [--git-dir=&lt;gitDir&gt;]
Git is a fast, scalable, distributed revision control system with an unusually
rich command set that provides both high-level operations and full access to
internals.
      --git-dir=&lt;gitDir&gt;   Set the path to the repository.
  -h, --help               Show this help message and exit.
  -V, --version            Print version information and exit.

Commands:

The most commonly used git commands are:
  help      Displays help information about the specified command
  status    Show the working tree status.
  commit    Record changes to the repository.
  add       Add file contents to the index.
  branch    List, create, or delete branches.
  checkout  Checkout a branch or paths to the working tree.
  clone     Clone a repository into a new directory.
  diff      Show changes between commits, commit and working tree, etc.
  merge     Join two or more development histories together.
  push      Update remote refs along with associated objects.
  rebase    Forward-port local commits to the updated upstream head.
  tag       Create, list, delete or verify a tag object signed with GPG.</pre>
</div>
</div>
<div class="paragraph">
<p>The description for the subcommand in the list is taken from the subcommand&#8217;s first <a href="#_header_and_footer">header line</a>, or, if the subcommand does not have a <code>header</code> annotation, from the <code>description</code>.</p>
</div>
<div class="sect3">
<h4 id="_hidden_subcommands">11.4.1. Hidden Subcommands</h4>
<div class="paragraph">
<p>Commands with the <code>hidden</code> attribute set to <code>true</code> will not be shown in the usage help message of their parent command.
See the <a href="https://picocli.info/#_hidden_subcommands">Hidden Subcommands</a> section of the user manual for details.</p>
</div>
</div>
<div class="sect3">
<h4 id="_help_subcommands">11.4.2. Help Subcommands</h4>
<div class="paragraph">
<p>Picocli has a <a href="https://picocli.info/#_built_in_help_subcommand">built-in Help subcommand</a>,
but see the <a href="https://picocli.info/#_help_subcommands">Help Subcommands</a> section of the user manual if you&#8217;re interested in creating a custom <code>help</code> command.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_reuse">12. Reuse</h2>
<div class="sectionbody">
<div class="paragraph">
<p>You may find yourself defining the same options, parameters or command attributes in many command line applications.
To reduce duplication, picocli supports both subclassing and mixins as ways to reuse such options and attributes.</p>
</div>
<div class="paragraph">
<p>One way to reuse the above option and attributes is to extend the class. Picocli will walk the class hierarchy to check for annotations, so <code>@Options</code>, <code>@Parameters</code> and <code>@Command</code> attributes declared on a superclass are available in all subclasses.</p>
</div>
<div class="paragraph">
<p>A command can also include a mixin by annotating a field with <code>@Mixin</code>. All picocli annotations found in the mixin class
are added to the command that has a field annotated with <code>@Mixin</code>. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="annotation">@Command</span>(name = <span class="string"><span class="delimiter">&quot;</span><span class="content">zip</span><span class="delimiter">&quot;</span></span>, description = <span class="string"><span class="delimiter">&quot;</span><span class="content">Example reuse with @Mixin annotation.</span><span class="delimiter">&quot;</span></span>)
<span class="directive">public</span> <span class="type">class</span> <span class="class">MyCommand</span> {

    <span class="comment">// adds the options defined in ReusableOptions to this command</span>
    <span class="annotation">@Mixin</span>
    <span class="directive">private</span> ReusableOptions myMixin;
    ...
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <a href="https://picocli.info/#_reuse">Reuse</a> section of the user manual has more extensive examples.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_parsing">13. Parsing</h2>
<div class="sectionbody">
<div class="paragraph">
<p>When parsing the command line, an application needs to take care of the following:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>If usage help was requested - show help message and exit</p>
</li>
<li>
<p>If version help was requested - show version information and exit</p>
</li>
<li>
<p>If the user input was invalid - show an error describing the problem and show the usage help</p>
</li>
<li>
<p>Execute the business logic</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>In Java code, that roughly looks like the below:</p>
</div>
<div class="admonitionblock tip">
<table>
<tr>
<td class="icon">
<i class="fa icon-tip" title="Tip"></i>
</td>
<td class="content">
In the next section we will show how to do the same in a single line of code, so keep reading&#8230;&#8203;
</td>
</tr>
</table>
</div>
<div class="listingblock">
<div class="title">Before</div>
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="predefined-type">Callable</span>&lt;<span class="predefined-type">Object</span>&gt; callable = <span class="keyword">new</span> MyCallable();
CommandLine cmd = <span class="keyword">new</span> CommandLine(callable);
<span class="keyword">try</span> {
    cmd.parse(args);
    <span class="keyword">if</span> (cmd.isUsageHelpRequested()) {
        cmd.usage(<span class="predefined-type">System</span>.out);
        <span class="keyword">return</span> <span class="predefined-constant">null</span>;
    } <span class="keyword">else</span> <span class="keyword">if</span> (cmd.isVersionHelpRequested()) {
        cmd.printVersionHelp(<span class="predefined-type">System</span>.out);
        <span class="keyword">return</span> <span class="predefined-constant">null</span>;
    }
    <span class="keyword">return</span> callable.call();
} <span class="keyword">catch</span> (ParameterException ex) {
    <span class="predefined-type">System</span>.err.println(ex.getMessage());
    <span class="keyword">if</span> (!UnmatchedArgumentException.printSuggestions(ex, <span class="predefined-type">System</span>.err)) {
        ex.getCommandLine().usage(<span class="predefined-type">System</span>.err);
    }
    <span class="keyword">return</span> <span class="predefined-constant">null</span>;
} <span class="keyword">catch</span> (<span class="exception">Exception</span> ex) {
    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="exception">ExecutionException</span>(cmd, <span class="string"><span class="delimiter">&quot;</span><span class="content">Error while calling </span><span class="delimiter">&quot;</span></span> + callable, ex);
}</code></pre>
</div>
</div>
<div class="sect2">
<h3 id="_runnable_and_callable">13.1. Runnable and Callable</h3>
<div class="paragraph">
<p>You can omit some of the boilerplate code from your application when the annotated object implements <code>Runnable</code> or <code>Callable</code>:</p>
</div>
<div class="listingblock">
<div class="title">After</div>
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java"><span class="predefined-type">Object</span> result = CommandLine.call(<span class="keyword">new</span> MyCallable(), args);</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>CommandLine.call</code> method returns the result of the <code>Callable</code>, or <code>null</code> if the command line options were invalid. An error message and a usage help message are printed when the command line options were invalid. Exceptions thrown from the <code>Callable.call</code> method are caught, wrapped in an <code>ExecutionException</code> and rethrown.</p>
</div>
<div class="paragraph">
<p>When the annotated object implements <code>Runnable</code>, use the <code>run</code> method. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java">CommandLine.run(<span class="keyword">new</span> MyRunnable(), args);</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_convenience_methods_for_subcommands">13.2. Convenience Methods for Subcommands</h3>
<div class="paragraph">
<p>If the command class has subcommands, the <code>CommandLine::call</code> and <code>CommandLine::run</code> convenience methods will execute the most specific subcommand on the command line. For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>&lt;command&gt; -g global_option subcommand -x -y -z subsubcommand param1 param2</pre>
</div>
</div>
<div class="paragraph">
<p>In the above example, the <code>subsubcommand</code> is the most specific subcommand, and only the <code>Runnable</code> or <code>Callable</code> associated with that subcommand will be executed by the <code>CommandLine::call</code> and <code>CommandLine::run</code> convenience methods.</p>
</div>
<div class="paragraph">
<p>The <code>CommandLine::parseWithHandler</code> and <code>CommandLine::parseWithHandlers</code> convenience methods are intended to offer the same ease of use as the <code>run</code> and <code>call</code> methods, but with more flexibility and better support for nested subcommands.</p>
</div>
<div class="paragraph">
<p>For example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="java">CommandLine cmd = <span class="keyword">new</span> CommandLine(MyTopLevelCommand())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">status</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitStatus())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">commit</span><span class="delimiter">&quot;</span></span>,   <span class="keyword">new</span> GitCommit())
        .addSubcommand(<span class="string"><span class="delimiter">&quot;</span><span class="content">add</span><span class="delimiter">&quot;</span></span>,      <span class="keyword">new</span> GitAdd());
<span class="predefined-type">List</span>&lt;<span class="predefined-type">Object</span>&gt; result = cmd.parseWithHandler(<span class="keyword">new</span> RunAll(), args);</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>CommandLine::parseWithHandler</code> method will take care of the following:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>parse the specified command line arguments</p>
</li>
<li>
<p>if the input was invalid, delegate to <code>DefaultExceptionHandler</code>, which will print the error message followed by the usage help message</p>
</li>
<li>
<p>otherwise, if the command line arguments were parsed successfully, let the specified <code>IParseResultHandler2</code> handle the parse result</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Picocli provides some default <code>IParseResultHandler2</code> implementations for common tasks:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>the <code>RunLast</code> handler prints help if requested, and otherwise gets the last specified command or subcommand and tries to execute it as a <code>Runnable</code> or <code>Callable</code></p>
</li>
<li>
<p>the <code>RunFirst</code> handler prints help if requested, and otherwise executes the top-level command as a <code>Runnable</code> or <code>Callable</code></p>
</li>
<li>
<p>the <code>RunAll</code> handler prints help if requested, and otherwise executes all commands and subcommands that the user specified on the command line as <code>Runnable</code> or <code>Callable</code> tasks</p>
</li>
</ul>
</div>
</div>
<div class="sect2">
<h3 id="_parser_configuration">13.3. Parser Configuration</h3>
<div class="paragraph">
<p>The picocli parser can be configured to be more strict or lenient.
You can instruct the parser to allow unknown options and other unmatched arguments, disallow POSIX clustered short options, and stop looking for options once a positional parameter or unmatched argument is found.
See the <a href="https://picocli.info/#_parser_configuration">Parser Configuration</a> section of the user manual for details.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_tracing">14. Tracing</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Picocli supports parser tracing to facilitate troubleshooting.
System property <code>picocli.trace</code> controls the trace level. Supported levels are <code>OFF</code>, <code>WARN</code>, <code>INFO</code>, and <code>DEBUG</code>. The default trace level is <code>WARN</code>.</p>
</div>
<div class="paragraph">
<p>Specifying system property <code>-Dpicocli.trace</code> without a value will set the trace level to <code>INFO</code>.</p>
</div>
<div class="ulist">
<ul>
<li>
<p>DEBUG: Shows details of the decisions made by the parser during command line parsing.</p>
</li>
<li>
<p>INFO: Shows a high-level overview of what happens during command line parsing.</p>
</li>
<li>
<p>WARN: The default. Shows warnings instead of errors when lenient parsing is enabled:
when single-value options were specified multiple times (and <code>CommandLine.overwrittenOptionsAllowed</code> is <code>true</code>),
or when command line arguments could not be matched as an option or positional parameter
(and <code>CommandLine.unmatchedArgumentsAllowed</code> is <code>true</code>).</p>
</li>
<li>
<p>OFF: Suppresses all tracing including warnings.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Example:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="CodeRay highlight"><code data-lang="bash"># create a custom 'mygit' command that invokes picocli.Demo$Git with tracing switched on
alias mygit='java -Dpicocli.trace -cp picocli-all.jar picocli.Demo$Git'

# invoke our command with some parameters
mygit --git-dir=/home/rpopma/picocli commit -m &quot;Fixed typos&quot; -- src1.java src2.java src3.java</code></pre>
</div>
</div>
<div class="paragraph">
<p>Output:</p>
</div>
<div class="listingblock">
<div class="content">
<pre>[picocli INFO] Parsing 8 command line args [--git-dir=/home/rpopma/picocli, commit, -m, "Fixed typos", --, src1.java, src2.java, src3.java]
[picocli INFO] Setting File field 'Git.gitDir' to '\home\rpopma\picocli' for option --git-dir
[picocli INFO] Adding [Fixed typos] to List&lt;String&gt; field 'GitCommit.message' for option -m
[picocli INFO] Found end-of-options delimiter '--'. Treating remainder as positional parameters.
[picocli INFO] Adding [src1.java] to List&lt;String&gt; field 'GitCommit.files' for args[0..*]
[picocli INFO] Adding [src2.java] to List&lt;String&gt; field 'GitCommit.files' for args[0..*]
[picocli INFO] Adding [src3.java] to List&lt;String&gt; field 'GitCommit.files' for args[0..*]</pre>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_tab_autocomplete">15. TAB Autocomplete</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Picocli-based applications can now have command line completion in Bash or Zsh Unix shells.
See the <a href="autocomplete.html">Autocomplete for Java Command Line Applications</a> manual for how to generate an autocompletion script tailored to your application.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_more">16. More</h2>
<div class="sectionbody">
<div class="paragraph">
<p>To keep this Quick Guide short (or at least, short-ish) some things had to be left out. Here are some quick links in case you are interested:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a href="https://picocli.info/#_picocli_in_other_languages">Picocli in Other Languages</a></p>
</li>
<li>
<p><a href="https://picocli.info/#_usage_help_api">Usage Help API</a> for customizing the usage help message layout</p>
</li>
<li>
<p><a href="https://picocli.info/#_tips_tricks">Tips &amp; Tricks</a></p>
</li>
<li>
<p><a href="https://remkop.github.io/picocli/apidocs">API Javadoc</a></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Don&#8217;t forget to star <span class="icon"><i class="fa fa-star-o"></i></span> the <a href="https://github.com/remkop/picocli">project on GitHub</a> if you like it!
Your stars keep me going! :-)</p>
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Version 3.9.6<br>
Last updated 2019-04-06 19:32:47 +09:00
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